1. Field of the Invention
The invention relates to a signal transfer unit for use in a physiological monitoring system. In particular, the invention relates to a portable signal transfer unit enabling transfer of physiological data from a physiological sensor attached to a mammalian subject in use, to a remote base station.
2. Description of the Prior Art
It is known to provide sensors for collecting physiological data from a patient and then to transfer the data from the sensor via wireless transmission to a remote base station unit for signal processing and storage. However, such systems locate the signal transmitter adjacent the sensor and, accordingly, the system as a whole and in particular the transmission unit is required to be lightweight precluding the use of transmission of too strong a signal or any data storage capacity thereby to ensure that the system is lightweight and attachable to the patient.
An example of the prior art includes WO94/01039 which provides a precordial system comprising a strip of sensors for detecting electrocardiographic data.
The system comprises a signal amplifier, encoder modulator and RF transmitter for relaying the data to a base station comprising a receiver module and suitable signal processing equipment to enable a clinician to monitor the cardiac rhythms of the patient. However, the precordial system must carry its own power supply for continuous use in running a transmitter which is capable of sending RF signals of a reasonable distance to the receiving unit. Such systems provide real dangers of losing data from a patient due to interruption in communication of the signal from the precordial system with the remote unit.
An object of the invention is to avoid or at least mitigate some or all of the problems of the prior art. One object of the invention is to provide a portable signal transfer unit operably in close proximity to or wearable by the patient remote from but proximal a physiological sensor, for example, by attachment to an external item of clothing worn by the patient, such as a belt. Another object is to provide one such unit adapted for use with multiple sensors, for example, located on different parts of a patient""s body such as on arms, chest and legs.
According to a first aspect of the invention, there is provided a portable signal transfer unit for relaying a signal representative of physiological data of a mammalian subject from a remote physiological sensor to a remote receiver unit, comprising an input device which operably receives the signal, a memory for buffering the signal and an output device which wirelessly transmits the signal to the remote receiver unit, such as a base station. Beneficially, the signal transfer unit can be somewhat larger than the physiological sensor itself and can be carried in a convenient location on the subject such as attached to a waist belt by using a clip on the signal transfer unit. As a result, sufficient power and memory can be provided within the signal transfer unit to enable relatively long term buffering and/or storage of a signal, for example, over several minutes or even longer than 30 minutes.
Preferably, the signal input device is adapted to receive a wireless transmission and can comprise two or more antennae for receiving the signal, and preferably three antennae are provided. Preferably, the three coils are substantially orthogonally arranged within the signal transfer unit. As a result of this configuration, satisfaction reception is established between the signal transfer unit and the remote physiological sensor.
In one embodiment, the signal input comprises a coil for inductive coupling with a transmission coil on a remote physiological sensor device. Preferably, three orthogonally arranged coils can be provided within the signal transfer unit and electrically conductive screening is provided between at least two of the coils and electrical components within the signal transfer unit, and preferably between each of the coils and electrical components within the signal transfer unit.
The output device can comprise a stub antenna or a plate antenna, for example. Where a plate antenna is used, this may be fairly large and therefore substantially equal to the surface area of the largest face of an outer casing for the signal transfer unit. The plate antenna can comprise a conductive track on a non-conductive substrate such as a copper track on a printed circuit board, for example. Preferably, the plate antenna is positioned adjacent the wall of the casing adapted to be adjacent the subject in use, which wall can for example comprise a clip attachable to a belt.
The signal transfer unit preferably comprises a signal amplifier stage and digital signal processing stage between the signal input and output device. Also, preferably a second input device enabling communication with the controller from a remote unit such as a base station is provided. The second input device can comprise a transceiver enabling both input and output of data and/or commands. For example, the second input device can comprise an RF receiver.
Preferably the units can comprise a subject interface including any one or more of the following: an on/off switch adapted to remove or enable power supply to the unit, an indicator such as a light to indicate the status of the power supply to the unit, an indicator such as a light to indicate whether a signal is being received from the physiological sensor device, an indicator such as a light to provide an indication of whether the unit is within range of the remote unit to enable transfer of the signal, a user output such as an audible alarm operable upon command from the remote unit, and preferably a switch to enable the user to deactivate the user output when appropriate.
The signal transfer unit can comprise a signal processor stage having one or more receivers for handling specified signal carrier frequencies.
According to an aspect of the invention there is provided a signal transfer unit for relaying signals representative of physiological data of a mammalian subject to a remote receiver unit, comprising a signal input for receiving the signal from a remote physiological sensor, an output device for transmitting the signal to the remote unit, and a signal processor for relaying the signal from the signal input to the output device, wherein the signal processor comprises one or more receivers each receiver adapted to handle a specified signal carrier frequency.
Preferably, first and second receivers are provided within the signal processor which first and second receivers are operable to handle different carrier frequencies. Alternatively, the first and second receivers are operable to handle the same carrier frequency.
The signal transfer unit can comprise a signal input having a first and second antenna and the signal processor can comprise a switch to ensure that the more usable signal from one of the first and second antenna is processed by the signal processor and output therefrom to the output device.
Preferably, the signal input comprises three or more antennae and the signal processor comprises a device for hunting between each of the three or more antennae to determine which antenna is receiving the most usable signal.
Preferably, the signal processor comprises a digital signal processor programmable to effect one or more virtual receivers for the signal.
According to another aspect of the invention there is provided a portable signal transfer unit for relaying a signal representative of physiological data of a mammalian subject to a remote receiver unit, comprising a signal input for receiving the signal from a remote physiological sensor, wherein the signal is in the form of a digitally modulated carrier frequency, an output device for transmitting the signal to the remote unit, and a signal processor for transferring the digital signal to the output device, further comprising a controller having a stored execution program for the digital signal processor and being operable to transfer the execution program to the digital signal processor when the portable signal transfer unit is initiated at start up.
A yet further aspect of the invention provides a signal transfer unit for relaying a signal representative of physiological data of a mammalian subject to a remote receiver unit, comprising a signal input for receiving the signal from a remote physiological sensor, an output for transmitting the signal to the remote unit, a controller for operably communicating the signal between the signal input and output device, and a physiological sensor which operably provides data representative of a physiological parameter of the subject to the controller in use, whereby the controller in turn incorporates the data into the signal for subsequent transmission by the output device.
In one embodiment, the signal transfer unit comprises an interface such as an RS 232 port to enable communication between the controller and a physiological sensor.
Also, it is possible for the physiological sensor to be incorporated within the signal transfer unit. The physiological sensor can comprise one or more of a motion sensor such as an accelerometer, a position sensor such as a mercury switch enabling determination of whether the subject is upright or lying down for example, and/or a microphone for monitoring the subject""s breathing sounds.
A yet further aspect of the invention provides a portable signal transfer unit for relaying a signal representative of physiological data of a mammalian subject to a remote receiver unit, comprising a signal input for receiving the signal from a remote physiological sensor, a memory for buffering the signal, an output device for transmitting the signal to the remote unit, and an indicator for indicating to the subject whether the signal transfer unit is within range of the remote unit to enable effective transmission of the signal from the signal transfer unit to the remote unit. Preferably, the signal transfer unit comprises a communication port for communicating with the remote unit. The communication port can comprise the output device adapted to receive signals from the remote unit. Beneficially, the remote unit can be powered using mains electricity and can therefore generate a stronger signal than the signal transfer unit. Accordingly, the remote unit can be configured to send a signal to the signal transfer unit to indicate whether or not a satisfactory signal is being received by the remote unit from the signal transfer unit.